Basic Oxygen Steelmaking is a process which employs the injection of oxygen into molten carbon-rich iron to obtain steel with relatively low-carbon content. The iron is processed in a furnace or, more specifically, in a Basic Oxygen Furnace (BOF) having a stout, oblong body lined with refractory material. The BOF is equipped with a taphole structure used for pouring of the finished molten steel through a tapping channel. The taphole structure comprises a tube-shaped removable refractory block consisting of several one after another equipped nozzles that forms in the mounted position the tapping channel which extends from the interior of the furnace and terminates in a casting or turret area of the furnace. Between the refractory block and a surrounding mantle of refractory material an annular gap is defined, which is filled with mortar or the like.
Due to wearing of the refractory block and it's lining refractory material, the refractory block must be removed and replaced relatively often, for example after about 40 to 120 tapping with each by emptying of the melt in the vessel.
The document DE-A-10 2010 056 117 discloses a handling of the replacement of a refractory block from the furnace's exterior. A filling opening, which is formed by a sleeve made of refractory material used in a perforation of the tapping channel with radial clearance, where the ring gap formed by the radial clearance is filled with refractory filler material. The sleeve exhibits an end of first circumferential collar located in the perforation of the tapping channel. The tapping channel near its target position facing the interior of the furnace, which bears the annular gap-bridging at the hole face of the hole provided with the sleeve at its outer end with a stopper-forming second collar and exhibits covered through-holes in the region of the annular gap. The refractory filler material for the annular gap is introduced through the perforations in the annular gap. With such a kind of filling of a viscous refractory material there exists the risk that the annular gap will not be filled completely.
Moreover a further important disadvantage exists in the fact that the inserting and positioning of the sleeve inside the tapping channel with the manipulator is connected with a difficult handling to reach an exact coaxial placement of the sleeve inside the channel.